During the current project period we intend to learn more about the potential mechanisms and consequences of the interaction of PMNs and plaque bacteria in reference to the etiology and pathogenesis of periodontal disease. We will attempt to define whether bacterial plaques of different ages vary in their capacity to stimulate PMN lysosome release. We will also determine whether PMN obtained during varying intervals during the development of experimental gingivitis differ in their responsiveness to plaque. We will learn more about the specific mechanisms whereby bacteria stimulate lysosome release by testing subcellular fractions of Gram-positive and Gram-negative microorganisms with PMNs. Lastly, we intend to ascertain if PMNs are able to kill representative plaque bacteria, as this may give some clues on the mechanisms of host resistance in the gingival crevice.